Field of the Disclosure
The present disclosure relates to an internal combustion engine, and more particularly to an internal combustion engine that, in accordance with an operating region, switches between a stoichiometric mode in which the engine performs operation at the theoretical air-fuel ratio, and a lean mode in which the engine performs operation at an air-fuel ratio that is leaner in fuel than the theoretical air-fuel ratio.
Background Art
JP 2003-239747A discloses a technique to suppress knocking. According to the technique disclosed in JP 2003-239747A, a knocking index that indicates easiness in the occurrence of knocking in an internal combustion engine is stored in association with operating conditions, and the flow rate of cooling water is controlled based on the knocking index determined in accordance with operating conditions.
Note that, in addition to the above described patent literature, JP 2011-149313A and the like may be mentioned as examples of literature describing the state-of-the-art at the time of filing the present application.